Form drawing of fluted tubing



Jan. 6, 1970 c; J. HOUSE 3,487,673

FORM DRAWING OF ELUTED TUBING Filed March 6 1967 8 8 8 w a o co m g l a: p 2 3 V 1: :3: :g: l i-w 0' 1 o INVENTOR AR ES J. HOUSE BY M? I ATTORNEY United States Patent O US. Cl. 72-282 8 Claims ABSTRACT OF THE DISCLOSURE Form drawing of deeply fluted tubing through a compound die in association with a stepped mandrel.

BACKGROUND OF THE INVENTION In form drawing of deeply fluted tubing such as from a 2% inch outside diameter tubing having .032 inch wall thickness, to tubing having an outside diameter measured to the crests of the flutes of approximately 1 /2 inches and having a flute height of approximately .140 inch, there has been a tendency for the tube to collapse and fold in an unpredictable manner causing breakage of the tube during initial metal formation. Delayed plugging was attempted but the sinking would not form true flutes. As the mandrel was subsequently advanced into the die opening breakage of the tubing would invariably take place.

SUMMARY OF THE INVENTION In accordance with the present invention tubing is drawn and fluted simultaneously in a manner which permits the formation of flutes of relatively great depth or height and at the same time provides an accurate control both of the inside diameter and outside diameter of the tubing at all points around its circumference, as well as an accurate control of wall thickness. This is accomplished basically by employing a compound die having a first section shaped to provide relatively shallow flutes in the tubing extending radially inwardly from its original cylindrical configuration, and a second or following fluted section having a tapered throat and provided with flutes dimensioned to provide the required outside dimension of the tubing. A compound mandrel conforming to the die sections is provided.

It is accordingly an object of the present invention to provide an apparatus and method characterized in the two-stage formation of flutes, the initial fluting being accompanied by sinking to a substantially reduced inside and outside diameter while at the same time increasing the depth of flutes to the required dimension.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawing, illustrating preferred embodiments of the invention.

BREIF DESCRIPTION OF THE DRAWING FIGURE 1 is an elevational view of a section of tubing showing the stages in its production.

FIGURE 2 is a transverse sectional view through the completed fluted tubing.

FIGURE 3 is a longitudinal section through the compound die and mandrel assembly, taken substantially on the line 3-3, FIGURE 4.

3,487,673 Patented Jan. 6, 1970 FIGURE 4 is a sectional view on the broken line 4-4, FIGURE 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGURE 1 there is shown an elevational view of a portion of a tube T. In this figure it is assumed that the drawing operation was terminated with the tubing in the die and the partially shaped and drawn tubing withdrawn. It will be observed that at the left the tubing has a plain cylindrical section 10 and at the extreme right end, as indicated at 12, it is deeply fluted as indicated at 14, and in addition is of substantially reduced diameter. Intermediate the sections 10 and 12 the partially fluted tubing tapers through a zone 16. It is to be noted particularly, that in a Zone 17 the flutes are initially formed in a cylindrical portion of the tubing by displacing material radially inwardly to form inwardly extending partially formed flutes without appreciable reduction in the major diameter of the tubing.

By way of a specific example the tubing in the production of which the present invention has proved particularly useful, reference is made to FIGURE 2 which shows dimensions of specific longitudinally fluted tubing having flutes 20 intermediate adjacent outwardly extending ribs 22, the flutes forming internally extending ribs 24 and the tubing having a major diameter measured to the crests of the outwardly extending ribs of approximately 1.500 inches, a minor inside diameter measured to the crests of the inwardly extending ribs of approximately 1.150 inches, giving an approximate flute height measured from the crests of the outwardly extending ribs to the crests of the inwardly extending ribs of approximately .175 inch, and having a wall thickness of .032 inch. This fluted tubing may be produced in accordance with the present invention from 2 /2 inch OD. x .032 wall, from -30 copper nickel tubing. In the specific example given sixteen flutes are provided but of course the number of flutes may be varied as required.

Referring now to FIGURE 3 there is illustrated at 30 a compound die which is supported in a die block of conventional arrangement, and associated with the die 30 is a compound mandrel 32 supported in the throat of the compound die by suitable means such as the mandrel support rod 34.

The first stage of the compound die comprises a ring 36 having a plurality of radially extending cylindrical openings 38 corresponding to the number of flutes to be formed in the tubing. Received in cylindrical openings 38 are short lengths 40 of cylindrical material such for example as drill rods, the radially inner ends of the rods being cylindrically rounded as indicated at 42. The drill rods are accurately adjusted to have their required inward extension and are clamped in position by suitable means such as set screws 44. At the downstream side of the ring 36 there is provided an annular locating collar 46 for purposes which will presently appear.

Surrounding the ring 36 is a mounting and assembly ring 48 provided with openings 50 through which extend assembly screws 52. Received beneath the heads 54 of the assembly screws 52 are washers 56, the radially inner edges of which overlies the ring 36 and which are adapted to clamp the ring in circumferentially adjusted position to provide for proper alignment between the flute forming surfaces provided by the rods and the flute forming 3 surfaces provided in the second section of the compound die.

The second section of the compound die is indicated at 58 and has threaded openings 60 for the reception of screws 52. At its upstream side, die section 58 is recessed as indicated at 62 to receive the collar 46 which constitute piloting means which retains the die sections 36 and 58in properly aligned position.

The inner surface of the die section 36 is cylindrical as best seen at 64, the fluting in this section being accomplished by the radially inwardly protruding ends of the rods 40. The second die section 58 has a tapered throat indicated generally at 66, the downstream section of the die being relatively deeply fluted and including a final flute forming section 67 of substantially uniform cross-section.

The compound mandrel indicated generally at 32 comprises the final flute forming portion 68 which is generally of uniform deeply fluted cross-section fitting accurately within the fluted section 67 through the die section 58. This mandrel section extends from an internally threaded connector 70 in which the mandrel rod 34 is threaded. Mounted on the mandrel is a preliminary flute forming section 76. This section may be formed of any suitable material, but excellent results are obtained when it is formed of nylon. The initial flute forming mandrel section 76 includes a collar 78 and may abut against an annular shoulder 79 on the final flute forming mandrel portion 68 or connector 70, and which may be retained in circumferentially aligned position thereon by suitable means such as a set screw 80.

With the foregoing described apparatus, an end of the relatively large tubing is first pointed and inserted through the compound die and connected to means for drawing the tubing through the die. As the tubing initially contacts the rounded ends 42 of the rods 40, the tubing is given an initial fluting of appreciable depth without however substantially reducing its outside diameter. Thereafter, the partially fluted tubing engages the tapered throat of the die section 58 at which time the tubing is sunk to approximately the required inside and outside diameter, and at the same time the flutes engage the corresponding fluted portions 67 of the die and 68 of the mandrel.

With this arrangement it will be observed that accurate control is maintained at all times of the instantaneous outside and inside surface dimensions of the tubing during fluting and sinking and that corresponding control of the wall thickness is maintained.

The invention is of course particularly applicable to the formation of deeply fluted tubing of relatively thin wall section as for example, between .020 and .050 inch. The method involves the application of the compound drawing steps to tubing of substantially greater initial diameter than the final average diameter of the fluted tube. In the specific example set forth in connection with FIGURE 2, the initial diameter of prime tubing was 2% inch OD. and the approximate average effective diameter (midway between the inside and outside diameter) of the final fluted tubing was approximately 1.222 inches. It will be observed that this represents a reduction to approximately half the initial dimension.

The drawing and the foregoing specification constitute a description of the improved form drawing of fluted tubing in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

1. A method of forming deeply fluted thin wall tubing which comprises initially progressively forming longitudinally extending flutes in said tubing intermediate outwardly projecting ribs primarily by progressive bending of the tube wall without substantial reduction in maximum outside tube diameter, and thereafter progressively substantially reducing the outside diameter of the tubing and deepening and shaping the flutes to required dimensions, producing the initial flute formations by drawing the tubing through an annular space defined between a first die having inwardly projecting flute forming portions provided with rounded ends, and a first fluted mandrel conforming to the rounded ends of the flute forming portions and spaced therefrom an amount substantially equal to the initial wall thickness of the tubing, and deepening and shaping the flutes by drawing the tubing through a substantially smaller annular space defined between a second die having a fluted opening provided with longitudinally converging rib and groove formations and with straight rib and groove formations parallel to the axis of the dies, and a second fluted mandrel having straight rib and groove formations parallel to the die axis and interfitting with the straight rib and groove formations in the second die.

2. Fluting die structure comprising a compound die having a first annular die section having an opening therethrough with an entrance and an exit end and provided with radially inwardly extending flute forming projections, a first fluted mandrel section within the opening through said first annular die section, said first mandrel section having alternated ribs and grooves extending parallel to the axis of the die, said die structure having a second annular die section directly adjacent said first die section and having an opening therethrough with an entrance and an exit end and being in aligment with the opening through said first die section, the opening through said second die section being shaped to provide adjacent the entrance end thereof a tapered throat having longitudinally converging rib and groove formations and adjacent the exit end thereof a straight flute forming portion comprising alternated ribs and grooves parallel to the axis of the die extending from said throat to the exit end of the opening through said second die section, the maximum diameter of the exit end of the opening through the second die section being substantially smaller than the exit end of the opening through said first die section, and a second fluted mandrel section in the opening through said second die section having on the portion thereof within the straight flute forming portion of the opening through said second die section straight ribs and grooves parallel to the die axis, said second mandrel section being substantially smaller in diameter than said first mandrel section. I

3. Structure as defined in claim 2 in which said first die section comprises an annular body having radial openings, radially adjustable rods in said openings, said rods having flute forming rounded ends projecting into the opening through said first die section in alignment with the grooves in said first mandrel section.

4. Structure as defined in claim 3, the second fluted mandrel section being of substantially uniform cross-section throughout said second die section.

5. Structure as defined in claim 2, said first fluted mandral section being rotatable relative to said second fluted mandrel section, and means for clamping said first man- =drel section in circumferentially adjusted alignment with said second mandrel section.

6. Structure as defined in claim 2, said first mandrel section being an externally fluted, annular body of a resin such as nylon.

7. Structure as defined in claim 2, an assembly ring surrounding said first die section in which said first die section is rotatable, assembly elements connecting said ring to said second die section, said elements including clamping portions engageable with said first die section to clamp it in circumferentially adjusted alignment against said second die section when assembly elements are tightened to secure said, ring to said second die section.

8. Structure as defined in claim 5 in which said die sections are in end abutment, and interfitting pilot means on said sections providing for axial alignment therebetween during relative circumferential adjustment.

References Cited UNITED STATES PATENTS Larson 72-283 Friedrich et al. 72-283 Cassady 72-276 Waisner 72283 Wright 72276 Durell 72-276 Wilcox 72-276 6 9/1936 McLaughlin 72282 11/ 1964 Lackinger 72283 FOREIGN PATENTS 3/ 1931 Germany. 2/ 1900 Germany.

CHARLES w. LANHAM, Primary Examiner ANDREW LEE HAVIS, Assistant Examiner US. Cl. X.R. 

